The determination of the exact hook position during the crane operation is an essential prerequisite for an automated crane control method.
Up to now, the height of the crane hook as a function of the radius from the crane, usually referred to as outreach, is calculated by geometric relations of the crane body. For this calculation, however, a rigid crane body is assumed.
During operation of the crane, the entire crane system or individual crane components is/are exposed to extreme loads caused by applied forces. The same however cause a considerable deformation of the geometric shape of the crane, which then leads to inaccuracies in the calculation of the position.
An increased need for safety during operation of the crane and particular crane operations regularly call for a determination of the position of the load lifting device as precisely as possible during the operation. In particular, a reliable lifting force limiter requires an exact determination of the hook position. In addition, a correct determination of the crane hook position is required in particular in a tandem operation of two cranes.
It is the object of the present disclosure to indicate a method for determining the current position of a load lifting device, which permits a more exact position determination as compared to the known methods.
This object is solved by a method for the control and/or data acquisition of a crane, wherein at least one measuring device at the crane supplies one or more measured values for determining the position of at least one load lifting device, for example a crane hook, wherein a calculation of the position of the load lifting device is effected on the basis of the one or more measured values of at least one measuring device and one or more data characterizing the stiffness of the crane.
Accordingly, the present disclosure is based on the fact that at least one measuring device at the crane supplies one or more measured values for determining the position of at least one load lifting device.
As load lifting device a crane hook preferably is used, but alternative load lifting device are conceivable, such as for example a supporting frame, a crossbeam, a grab, a magnetic lifting means, etc.
According to the present disclosure, a calculation of the exact position of at least one load lifting device is effected on the basis of the one or more measured values of at least one measuring device and one or more data characterizing the stiffness of the crane. Preferably, among the data characterizing the stiffness of the crane, values generally are meant which describe a deviation of the crane geometry during operation of the crane from the normal rigid form of the crane.
In this connection, data characterizing the stiffness of the crane in particular comprise data which relate to the bending and/or tensile and/or torsional stiffness of the crane or certain crane components or provide a measure for the bend and/or elongation and/or torsion of the crane or certain crane components.
It is also possible to consider a spring constant of the crane or a crane component as the data characterizing the stiffness of the crane.
Accordingly, the method turns away from the previous assumption of a rigid crane structure and instead considers influences on the crane structure, in particular the effects of the applied forces on the crane geometry and the related deformation of the geometric crane shape, in order to provide for a more precise determination of the position of the load lifting device.
The position of the load lifting device preferably is calculated in radial direction R to the crane and in vertical direction V relative to the crane or as absolute value in vertical direction H.
Data characterizing the stiffness of the crane preferably relate to the bend or bending stiffness of at least one crane component. Possible crane components in this connection include the crane tower or individual tower elements as well as the boom system or individual boom elements.
Furthermore, the data characterizing the stiffness of the crane may consider the suspension of one or more crane components. In this connection, at least one outrigger of the crane should be mentioned. In particular, the suspension of at least one support arm and possibly the suspension of the support mechanism, for example of the corresponding support cylinder, should be taken into account.
Said crane components are subject to deformations which can be determined in dependence on the suspended load mass and position.
The data characterizing the stiffness, in particular the tensile stiffness, of the crane also can include the condition of at least one hoisting cable. Here, the total stiffness and in particular the cable sag and/or the cable elongation and/or the tensile stiffness of at least one hoisting cable can contribute to an improved representation of the crane system and help to achieve a more precise position determination of the load lifting device used.
One or more data characterizing the stiffness of the crane preferably can be detected by one or more suitable measuring devices during operation of the crane and be employed for calculating the position of the load lifting device.
Alternatively, a crane model considering the crane stiffness can be generated and be taken into account for the calculation of the position of the load lifting device. For example, the calculation of the position of the load lifting device can be based on a real-time model being simulated in the crane controller, the model including the crane stiffness. Modeling the crane condition involves the advantage that a limited number of sensors is sufficient for the exact determination of the position of the load lifting device. By using deformable crane models, a more realistic calculation can be achieved.
For modeling, one or more crane components for example can be represented as elastic elements, preferably beams. Due to the realistic modeling of the crane system, the bend of the elements or beams is considered in the calculation of the position of the load lifting device.
For example, one or more tower elements of the crane are interpreted as beams whose bend is simulated in a known way. In addition, the elements of a boom system preferably can likewise be understood as individual beams whose deflection can be determined.
Expediently, the support system, in particular individual support arms or associated support cylinders are modeled as resilient or damping elements.
Furthermore, extensible elements can be employed for generating a crane model, wherein the extensible elements in particular represent the condition of at least one hoisting cable. Preferably, a possible cable sag and/or a possible cable elongation of at least one hoisting cable thereby is considered in the crane model.
For determining the position of the load lifting device certain parameters describing the crane condition may be required. Preferably, at least one measuring device arranged at the crane detects the suspended load mass. In addition, the boom erection angle can metrologically be detected, in particular by means of at least one measuring device arranged at the crane and provided for this purpose. Of course, the crane inclination—for example when mounted on a ship—also can be detected, in order to take account of the same.
As has already been explained above, the exact position of the load lifting device is described by the radial distance R to the crane and the vertical height H of the load lifting device. The bend of the boom system and/or the bend of the crane tower and possibly the spring or damping movement of the supporting device can be calculated for example by taking into account the load mass and possibly the boom erection angle. In this case, load mass and/or boom erection angle expediently are determined directly or indirectly by measurement.
The radial distance R of the load lifting device to the crane then can be determined with reference to the measured values and the calculated or modulated bend or spring and damping movement, in particular be derived from the previously determined values by means of transformation.
In one embodiment of the method it is conceivable that at least one measuring device detects the unwound hoisting cable length.
The cable elongation and/or the cable sag of at least one hoisting cable can be calculated or modeled in dependence on the detected value for the unwound hoisting cable length and taking into account the determined distance R. The height H of the load lifting device then can be derived from the calculated values, in particular by calculations.
The method of the present disclosure accordingly provides for a particularly exact determination of the coordinates R and H. The method requires no installation of additional sensors, but the position determination can be carried out by means of the usual sensors.
In principle, it is possible to metrologically detect individual model parameters and/or derive the same with reference to certain measured values. It may be expedient to detect the bend of the crane tower or the boom system by suitable measuring device. The same applies to parameters which characterize both resilient or damping elements and/or extensible elements.
An exact position determination of the load lifting device in particular is desirable in so-called multi-crane controllers, as in these cases minor deviations of the actual position of the common load or load lifting device from a position determined by the controller can lead to a considerable endangerment of the crane operation. The method according to the present disclosure is suitable in particular for controlling a tandem crane system. Furthermore, the use of the method according to the present disclosure is expedient in particular when implementing grab controllers or lifting force limiters.
The present disclosure furthermore relates to a crane controller for a crane for carrying out the method described above. Accordingly, the advantages and details of the method according to the present disclosure quite obviously apply to the execution of the crane control according to the present disclosure, which is why a renewed description will be omitted at this point.
Furthermore, the present disclosure is directed to a crane with such crane controller. Accordingly, the advantages and properties of the method according to the present disclosure analogously apply to the design of the crane according to the present disclosure.
It is particularly advantageous when at least one measuring device of the crane includes one or more DMS elements. The arrangement of individual strain gauges at the crane system allows an easy detection of the deformation, in particular bend, of certain crane components. In particular, the arrangement at the boom system or at individual elements of the boom system is expedient. In addition, the use of one or more strain gauges at the crane tower is suitable to detect the bend of the crane tower or individual crane tower elements.
It is furthermore advantageous when at least one measuring device comprises a sensor unit arranged at the retracting mechanism. Such sensor unit allows the measurement of the unwound cable length, which is taken into account in particular for calculating the height H of at least one load lifting device, in particular of a crane hook. Respective measured values likewise or alternatively can be supplied by one or more cable pulleys.
In addition, a sensor unit expediently can be provided at the luffing gear, in order to measure the condition of the luffing gear or the luffing angle of the boom system. What is also possible is an angle sensor which is mounted at the boom system or at the luffing joint and detects the actual erection angle of the boom system.
A further subject-matter of the present disclosure relates to a tandem crane system which consists of at least two cranes. According to the present disclosure, at least one crane or the entire tandem crane system includes at least one crane controller according to any of the advantageous embodiments described above. Two or more cranes preferably are operated by a uniform crane controller and hence can simultaneously be controlled by a crane operator.
The present disclosure furthermore relates to a data carrier with a stored software for a crane controller, which is suitable for carrying out the method according to the present disclosure or an advantageous embodiment of the method according to the present disclosure. The advantages and properties of the claimed data carrier hence correspond to those of the method according to the present disclosure.
Further advantages and details of the present disclosure will be described in detail with reference to the following drawings.